1. Field of the Invention
The present invention relates to crucibles, and in particular relates to stackable crucibles and systems for using stackable crucibles in furnaces.
2. Description of Prior Art
Thermogravimetric analyzers (TGA) are used to analyze moisture, volatiles and ash (coal and coke). Some systems have multi-sample capabilities and/or crucible covers for allow the analysis of several samples simultaneously. Automation and computer control allow increased productivity. Automatic crucible cover placement and removal during the analysis of volatiles makes the instrument fully automatic and reduces the risk of sample oxidation, while also providing better repeatability of the volatile matter results.
U.S. Pat. No. 7,048,888 to Las Navas Garcia discusses an automatic cover system for proximate analyzers and the like. An apparatus is provided to automatically cover and uncover crucibles according to a predetermined procedure in a proximate analyzer. A series of crucibles mounted in a first carousel is heated in a furnace. A second carousel mounted above the first carousel holds crucible covers. A mechanism synchronizes the movements of the carousels so that the heated crucibles are automatically covered and uncovered at the appropriate times during the analysis with a corresponding cover by lowering or raising the second carousel. The movements of both carousels are automatically controlled so that at appropriate points in the testing cycle they rotate simultaneously about a common central axis and a crucible is deposited on a weighing platform by controlling the vertical motion of the entire carousel apparatus. The crucible is weighed either with or without a crucible cover depending on the stage of the analysis without the need of manual intervention. The specification of U.S. Pat. No. 7,048,888 is incorporated herein by reference.
U.S. Pat. No. 7,172,729 to Las Navas Garcia discusses a mixed sample moisture or ash analyzer. In particular, an analyzer for moisture or ash testing is provided where a robotic arm retrieves a crucible and sample from a conveyor, inserts it into a small opening in the upper surface of the furnace chamber and deposits it in an aperture on a carousel located within the furnace chamber. The carousel in the furnace chamber manipulates the crucibles within the furnace chamber. The opening in the upper surface of the furnace chamber is positioned such that when the carousel is ready for loading or unloading, an aperture in the carousel for holding the crucibles is aligned with the opening. At appropriate points during the testing cycle, individual crucibles are automatically deposited on a weighing platform connected to an internal balance through vertical motion of the carousel. Once final weighing in the test cycle is performed, the crucible is removed through the opening on the upper surface of the furnace chamber by the same robot arm which placed it in the chamber. The specification of U.S. Pat. No. 7,172,729 is incorporated herein by reference.